Atypical lymphocytic lobular panniculitis

Background: Although subcutaneous T-cell lymphoma (SCTCL) is considered an aggressive form of lymphoma, some patients manifest a long waxing and waning phase unaccompanied by constitutional symptoms. Methods: Twelve patients were prospectively encountered, presenting with a lymphocytic panniculitis accompanied by lymphoid atypia, although not fulfilling criteria for SCTCL. Clinical, histologic, phenotypic, and genotypic analyses were conducted. Results: There were five men, one boy, and six women; none had symptoms compatible with lupus erythematosus or aggressive SCTCL. All but two had a waxing and waning course of years. Four patients had periodic cytopenias accompanied by fevers. While responding somewhat to prednisone, the lesions relapsed. In one patient, treatment with alemtuzumab (CAMPATH-1) led to complete lesional resolution with no recurrence. Light microscopy showed expansion of the interstices of the fat lobule by mildly atypical lymphocytes of the CD4 subset in 10 biopsies from eight patients; in the other four patients, there was an increase in CD8 lymphocytes. There was diminished expression of CD5 and/or CD7 in the majority of biopsies. Ten of 13 biopsies showed clonal T-cell receptor-gamma rearrangements. conclusions: We apply the term atypical lymphocytic lobular panniculitis to this distinctive form of lymphocytic panniculitis manifesting this light microscopic, phenotypic, and genotypic profile.